Short range wireless communication systems have been used previously to provide communications between electronic devices and broadcast receivers. As with many communication systems, power and bandwidth are fundamental resources for such short range wireless communication systems, and these parameters can be selected to determine the performance and power requirements of a short range wireless communication system. Typically, the transmitter power is selected to be low so as to limit its range and its power requirements. One problem associated with these short range broadcasts to a broadcast receiver, however, is that interference from external broadcasts will interfere with the broadcast from the short range transmitter. It is desirable, therefore, to identify and select a channel that is not being used.
To identify open channels, one current system provides an RF (radio frequency) modulator to convert a composite signal to an RF channel selected using a scanning receiver. The scanning receiver locates RF channels that are not in use by broadcast stations in a particular geographic area. These unused stations are identified by determining channels having signal-to-noise ratios below a threshold value indicative of an open or unused channel. When used for short range broadcasts, such unused channels typically do not exhibit the hissing or muting associated with a channel containing even a weak external broadcast signal. Unfortunately, unused channels are becoming increasingly difficult to locate due to the overpopulation of broadcast stations occupying the set number of channels available.
Some current devices, such as portable music players, portable DVD players, and other electronic devices, are often combined with OEM (original equipment manufacturer) or after-market electronics that allow the devices to transmit media content on broadcast channels within a frequency band. One example of such a solution is the use of an FM transmitter in combination with portable media players to allow the media content to be broadcast from the portable device to a local receiver through short range FM broadcasts.
One common environment in which FM transmitters are often utilized is with respect to automobile electronics. A portable music player, satellite receiver, DVD player, or other electronic device can transmit media content to the car entertainment systems through FM transmissions so that wires are not needed. For example, an FM broadcast receiver within a car can be tuned to an open channel, and an FM transmitter can be tuned to transmit on this same channel. As such, the audio content on the portable player can be played through the car's audio system. Unfortunately, external radio broadcasts can interfere with this process, especially if a user is traveling by car, for example, while using such a device and coming within range of different broadcasts over the FM band.
Because unused or open channels are becoming more and more difficult to find, an improved short range transmission system is needed for allowing a user to better determine and select what channel or channels to use when employing short range broadcasts.